1. Field of the Invention
This application relates to musical instruments and, in particular, to steelpan drums.
2. Description of the Related Art
The steelpan is considered as a traditional art form in the country where it has originated, namely the Republic of Trinidad and Tobago, where it has been proclaimed as the National Instrument. In its bearing on the evolution of the present invention, the prior art is completely defined by the conventional traditional acoustic steelpan musical drum instrument. The acoustic steelpan or traditional steelpan is an instrument which presents well-defined note playing areas of definite pitch, on one or more continuous metal note bearing surfaces, hereinafter also referred to as playing surfaces.
The heretofore mentioned instrument is played in percussive mode and was first invented in the island of Trinidad in the Republic of Trinidad and Tobago, some time in the late 1930s. The exact date of invention is unknown as the origins of the instrument are steeped in folklore, having been first fashioned by individuals who were mostly working class and generally technically illiterate. However, the first published report of the instrument was printed in the Trinidad Guardian newspaper on Feb. 6, 1940.
As forerunners of the present invention, the first steelpans were fashioned from the empty oil drums abandoned by the US army and are still largely made from what is known to those skilled in the art of steel container manufacture, as tight head cylindrical steel barrels or drums. Said drums are manufactured by cold rolling the top and bottom heads to the cylindrical body of the drum or barrel. The joint thus formed is known by those skilled in the art of steel container manufacture as a chime.
In its relation to the present invention, the playing surface is fabricated by first manually sinking and forming one of the drum heads with a hammer or impact tool and or press forming equipment. Musical note playing areas are then clearly defined on the note bearing surface by the formation of grooves. The aforementioned note bearing surface is then heat treated and cooled. Subsequently, the said note areas are tuned by carefully and skillfully hammering them into the required shape by a Pan Tuner, to create areas that produce musical notes of definite pitch when struck.
The cylindrical body of the original drum is retained to form what is known as the skirt of the steelpan but is cut to various lengths primarily to perform the role of an acoustic resonator. The circular playing surface typically ranges from 55.88 cm/22 in to 68.58 cm/27 in in diameter and the length of the skirt ranges from about 15.24 cm/6 in to 91.44/36 in. Larger and smaller sizes have been used but the implementations that have been adopted utilize the stated ranges presumably for reasons of ergonomics and performance facilitation.
In their influence on the development of the present invention, drums which are formed as described above, are grouped to form a variety of steelpan instruments to cover different parts of the musical range. As such, a steelpan instrument is a musical instrument in which the notes are distributed over a number of drums. The number of drums in a steelpan instrument is dictated by the limitations of the applicable laws of science that determine the size of note area required to resonate at desired musical note frequencies.
There are at least eleven steelpan instruments in the traditional steelpan family. The nine-bass steelpan consists of nine drums with three notes each for a total of 27 notes typically ranging from A1 to B3. The more common six-bass steelpan consists of six drums with three notes each for a total of 18 notes typically ranging from A1 to D3. Tenor bass steelpans consist of four drums to typically cover the range G2 to D4. Cello steelpans cover the baritone range and come in two varieties. The 3-cello steelpan typically covers the range B2 to G4 over three drums while the 4-cello steelpan typically covers the range B2 to D5 over 4 drums.
The quadraphonic steelpan is a recent innovation that uses 4 drums to cover the range B2 to B♭5. The double guitar steelpan uses two drums to cover the range C♯3 to G♯4. The double second steelpan uses two drums to cover the range F3 to B♭5. The double tenor steelpan uses two drums to cover the range A3 to C♯6. The Low tenor uses a single drum to cover the range C4 to E♭6. The high tenor uses a single drum to cover the range D4 to F6. For historical reasons, an anomaly exists in the naming of the tenor pan which actually carries notes in the soprano range.
In order that the pan player may obtain good musical quality, the end of the stick or mallet that is used to contact the note bearing surfaces is covered, wrapped, or coated with a soft material, usually of the consistency of rubber. If the material used is too hard, the sound produced tends to become dissonant and harsh. If the material used is too soft, the sound produced becomes muffled. Thus the design of the stick determines the time that the stick remains on the note at the point of impact, defined as the contact time. Note partials that have frequencies with cycle periods shorter than the contact time are suppressed while those possessing frequencies with cycle periods longer than the contact time are not.
The playing surface of the very first steelpans was of a convex shape. However, this provided some difficulty in performance. As the instrument evolved, pannists and steelpan tuners showed strong preference for the concave shape which has now been adopted universally as the norm.
As it relates to the background art, in current steelpan designs, the playing surface is fashioned by hammering one flat end of the drum into a concave bowl, thus stretching the metal to the required depth and thickness. This said process is called “sinking.” The sinking process reduces the thickness of the playing surface and adjusts the material elasticity to levels required to support the desired note range. The sunken surface is then separated from the rest of the drum by cutting the skirt at an appropriate distance beneath the rim of the sunken end. The other half of the drum is either discarded or used to make a separate steelpan.
Note bearing areas may now be demarcated, often by engraving grooves or channels between note areas with a punch. This step is not absolutely necessary and serves only as a means for pannists to easily identify note areas. What is more important is the degree of separation and isolation between the notes; this is essential to a good sounding instrument as it provides an acoustic barrier which reduces the transmission of vibration energy between notes thus improving the accuracy of the instrument. For the purpose of clarification, accuracy refers to the characteristic of the instrument which facilitates the production of the intended musical note and only the intended notes, when the pertinent note bearing area is excited.
Trinidad and Tobago patent No. 33A of 1976 (expired) to Fernandez, the “magno pan” was the result of magnetic tuning of steel drums by magnets contacted to each note in a particular way, so that when the magnets of different magnitudes are regulated to specific areas of the notes, the pans can be altered from one key to another key, by as much as two tones apart i.e. C to E, or E to C. The quality of tone can also be altered by regulation of the magnets. Trinidad and Tobago patent No. 32 of 1983 (expired) also to Fernandez, the “bore pan”, enhances the barrier by boring holes along the note area perimeter and heat treating the area around the note.
On the note bearing surfaces of the steelpan, note separation refers to the degree of isolation of one note from another; in poorly separated notes, a significantly large percentage of the energy imparted by a strike to one note is transmitted to another, so much so that the sound generated by the second note is discernible. Poor separation can result in unwanted excitation of groups of notes.
Consonance and dissonance are terms used to describe the harmoniousness and pleasantness of the composite sound produced when two or more notes are simultaneously excited, a distinct possibility on the steelpan on which multiple notes share the same surface and multiple notes can be accidentally excited through energy coupling as described above. Consonant tones sound pleasant while dissonant tones sound unpleasant. As such, the concept of consonance and dissonance is a bit subjective.
It is generally accepted that dissonance results when partials from two notes fall within a critical band of frequencies. Although the range of this band varies along the musical scale, it typically ranges from about 30 Hz to 40 Hz. Thus consonance and dissonance are directly related to musical intervals and, as such, there are levels of consonance that arise in any musical scale. In particular, in Western music, the consonance of musical intervals is graded in decreasing consonance or increasing dissonance.
Intervals corresponding to octave (most consonant), perfect fifth, perfect fourth are said to be in perfect consonance, while intervals corresponding to major sixth, major third, minor sixth and minor third are said to be in imperfect consonance. The most dissonant intervals, in decreasing levels of dissonance, are generally considered to be the minor second (most dissonant), major seventh, major second, minor seventh, and the tritone (augmented 4ths or diminished 5ths).
Dissonant sounds can be produced if some energy from a note that is struck is transmitted to another note that has overtones that are not in consonance with the struck note. It is for this reason that chromatic arrangements of notes on the playing surface are generally avoided as all notes will then be a minor second apart.
As it relates to the present invention, it must be emphasized that tuners capitalize on inter-note coupling to vary the overtones produced by each note. This is done by selective adjustment of tensions in the area between the notes and by judicious arrangement or layout of notes on the playing surface of the instrument to ensure that most of the coupling occurs between consonant groups of notes.
For the present invention, the note separation problem lies at the heart of the challenge of devising a note layout schema that determines the value and location of notes on a steelpan drum. A plurality of note layout schemas has been used over the years.
As it has affected the evolution of the prior art over the years, pannists have demonstrated preference for particular given physical note arrangements. The preferred arrangements are listed in standards published by the Trinidad and Tobago Bureau of Standards. Most notable of these is the fourths and fifths arrangement for use on the tenor steelpan which has been found to facilitate musical performance while minimizing dissonance on that said instrument. Adjacent notes on said layout, being generally the notes that will experience the greatest degree of energy coupling, are set to musical intervals of the octave, fourths or fifths, these being the four most consonant musical intervals.
After note demarcation, the drum is heated to about 300° C. to relieve the mechanical stresses developed in the sinking process. The steelpan is then cooled either quickly by quenching or more slowly in air. Variations in the heating process vary from one manufacturer to another. Next, individual notes are formed by careful hammering of the selected areas. Finer adjustments are made in the size and shape of the note areas to define the note pitch and partials. Tuning of the steelpan is an iterative process and is accomplished either by ear or with the aid of mechanical or electronic tuning devices.
The steelpan musical instrument of the prior art allows for some variation of timbre or voice because a tuner can individually tune the partials of any given note. This process is known as “harmonic tuning”. In essence, then, the steelpan is a mechanical means of implementing sound synthesis. Harmonic tuning also benefits the player who can thereby create further subtle variations in note timbre by striking of the note bearing surfaces in different locations.
For the prior art, the skirt of the said traditional acoustic steelpan takes the form of a tube or pipe, of diameter equal to the playing surface. Its role in effecting acoustic coupling and projection of the sound created by vibration of notes on the playing surface can be described by rigorous application of well known principles of acoustics. The required analysis is quite complex but can be simplified for the purpose of this document through consideration of two primary mechanisms.
Firstly, the steelpan drum can be modeled as a tube that is closed only on one end. This is known to those skilled in the discipline of acoustics as a closed-open tube and displays resonances characteristic of the air enclosed in the barrel. An ideal closed-open tube has a fundamental resonance at
      f    1    =      v          4      ⁢              (                  L          +                      0.3            ⁢            d                          )            
where d is the tube diameter, L the tube length and v the velocity of sound in air. The factor 0.3d is an end correction factor used to compensate for dispersion of the sound at the end of the tube. The factor L+0.3d therefore corresponds to a ¼ wavelength of the fundamental resonance frequency.
In its bearing on the prior art, what is of significance to the steelpan, is the fact that the ideal closed-open tube also displays resonance peaks at odd multiples of the fundamental resonance frequency and resonance nulls at even multiples of the fundamental resonance frequency. In practice, the frequency response of a tube will display maxima at odd multiples of the fundamental resonance frequency and minima at even multiples of the fundamental resonance frequency.
The strength of the displayed resonances and correspondingly, the difference between frequency response maxima and minima, become more pronounced as the ratio of radius to skirt length decreases. As such, the contribution of the resonance effect increases for steelpans of lower pitch that typically carry long skirts.
In addition, sound is propagated from the walls of the skirt itself in response to acoustic energy transferred from the playing surface through the rim to the skirt. Whereas the skirt is naturally characterized by its own modal behavior defined by characteristic modal frequencies at which it resonates, it would also vibrate at the frequencies produced by the note bearing areas on the playing surface as well. The strength of these vibrations would depend on how hard the notes are struck and how close the component frequencies of the resultant vibrations on the playing surface are to the resonant frequencies of the skirt.
Frequency components that are closest to a skirt resonant frequency will tend to experience greater amplification in vibration level than those that are not. The net contribution to the sound field by the skirt would be as a result of the composite effect of these vibrations over the entire area of the skirt. In particular, although vibration levels at any given point of the skirt would generally be small, the resultant contribution over the large surface area of the skirt would lead to a level of sound that is quite discernible.
For the high tenor steelpan, the skirt of the drum from which the pan is made is cut to a length of 11.60 cm/4 in to 15.24 cm/6 in. The length of this aforementioned skirt increases as one goes down the musical range, reaching a typical length of 86.36 cm/34 in for the six-bass. In the final stage of the process the said instrument is given a protective coat. This may include paint, an electroplating finish, usually nickel or chrome, or sprayed and baked plastic finish. Minor adjustments in tuning are often required after this process.
The perimeter of the said playing surface of the steelpan, which is called the rim in the steelpan fraternity on the traditional acoustic steelpan, corresponds to what is known as the chime by those skilled in drum and barrel container manufacture and is made by crimping or rolling the materials comprising the playing surface and skirt. When the playing surface of a traditional steelpan is struck during a performance, some of the impact energy excites one or more torsion modes of the drum. For the 55.88 cm/22 in diameter drums used on most traditional steelpans, with the rim as described above, said torsional vibration has a subsonic frequency component of about 15 Hz. Said vibration is significant for normal performance impacts and can actually be felt when one touches the rim of the instrument.
The consequent fluctuating shape distortion of the playing surface on the traditional steelpan drum due to the torsion mode of vibration is largely responsible for the changes in note pitch frequency which occur at times, particularly on the notes closest to the edge of the playing surface, and therefore negatively affects note clarity and accuracy. Moreover, traditional steelpans go out of tune if the rim of the instrument is distorted due to stress caused by an externally applied force or temperature changes.
By dint of a paradigm shift, the invention and ongoing development of the steelpan musical instrument, apart from fostering the export of the steelpan instrument from a developing country to many first world countries has ushered in a new era of metallurgical technology globally. Until its invention in Trinidad and Tobago in the 1940s, musical instruments made from steel shells and steel plates were relegated for use only as rhythmic instruments such as gongs, cymbals and bells.
Dynamically however, the advent of the steelpan musical instrument has added to the global repository of metallurgical technological knowledge, by demonstrating convincingly that it is possible to produce high quality melodic tones, through controlled deformation and treatment of steel sheets and meticulously careful design of the sticks or mallets used for performance, in the striking of respective note bearing surfaces. The term “steelpan technology” has been coined in Trinidad and Tobago out of the dire need to codify and encapsulate the complex metallurgical processes involved.
There are many easy and obvious extensions to the traditional practice of steelpan fabrication. The instrument needs not be fashioned from an oil drum as was done traditionally. Indeed the entire instrument can be made from sheets of metal by fashioning and attaching a metal top, which will ultimately form the playing surface, to an appropriately shaped support. Attachment can be achieved by welding or crimping, for example. Sinking can and has been achieved by a variety of standard industrial processes such as hydro-forming or spin-forming.
Despite its novelty and appeal, the traditional acoustic steelpan instrument suffers from several disadvantages. Firstly, the musical range of each steelpan in the traditional family of steelpans is typically less than three octaves. This is a limitation, particularly for soloist performances that is often compensated for by transposition of portions of a composition, the required notes of which fall outside the range of the instrument being played. In addition, some performers make up for this deficiency by simultaneously performing with two different steelpan ranges.
Furthermore, as existing steelpans evolved in a generally ad hoc manner, dependent upon need, there is an apparent clutter due to the fact that at least eleven instruments were required to cover the entire musical range. This clutter is further compounded when one considers the plethora of variations in note layout styles.
Said variations in note layout styles also contribute to the difficulty experienced by individuals, who may wish to play a wide range of steelpan instruments in an orchestra. Moreover, it works against player mobility, said mobility being the ability of a player to play in different steelpan orchestras which have steelpans with differing note layouts.
The traditional method for acoustic steelpan manufacture, relies on the steel container manufacturing industry for its primary raw material, said raw material being a finished used or unused steel drum, usually of the 55 gallon variety. However, drums made by said steel container manufacturers are designed strictly for the container market for which the primary concern is the ability of a drum to resist bursting when subjected to impact stress. As such, said manufacturers are less concerned with the metallurgical properties of the steel used to manufacture drums, than they are with its tensile strength. As such, the steel used in traditional manufacture can have widely varying metallurgical characteristics, such as Carbon content, grain size and purity, required to make a high quality steelpan musical instrument. This clearly impacts on the variation of musical quality of the steelpan instrument made from such drums.
In addition, as traditional drums are largely manufactured from barrels made for the container industry, traditional steelpans are not of optimum design, said design being characterized by consideration of the required characteristics of the major parts of the steelpan for the creation of an instrument of the highest musical accuracy and rendition. Said major parts are the playing surface, the chime and the skirt.
In the manufacture of the traditional acoustic instrument, little or no attention is paid to the need to modify or adapt the chime and skirt to optimize performance. Moreover, the playing surface is only shaped with the sole intent of defining musical note areas. These said three components can detract from the musical accuracy of the instrument as they resonate at their own natural structural modal frequencies when the instrument is struck during a performance. Said modal frequencies have been measured at as low as 15 Hz. As these natural modes of vibration are associated with modal deformations of the playing surface, the geometry of the notes defined therein is distorted resulting in low frequency modulation of the note frequencies.
In addition to the modulation effect, the non-musical vibrations of the skirt, in particular, contribute to noise that detracts from musical quality. In particular, high frequency resonances can often be discerned when a note is struck and very often even after the musical components of the generated sound have substantially decayed. These resonances are generated primarily from the parts of the playing surface that are not tuned as note areas, from the chime and from the skirt. This is a pertinent issue with the traditional steelpan which requires resolution and has been readily identified by varied experts with keen musical ears.
As well, the frequency response of the closed-open tube that forms the skirt has maxima at odd multiples of the first resonance and minima at even multiples of the first resonance. Moreover, the difference between maxima and minima increases as the ratio of barrel radius and length decreases. Said radius/length ratio typically varies from 0.32:1 for the bass to 1.83:1 for the tenor steelpan. Thus, although a stronger resonance exists for the bass instruments, the frequency response of the closed-open tube of which it is formed is much more uneven than for the higher pitched instruments that use shorter skirts. This can have deleterious effects on tonal structure.
By comparison, the resonance effect that arises from the characteristic uneven frequency response of the closed-open tube design used in wind instruments such as the clarinet or flute is absolutely essential for the generation of notes and their corresponding harmonic overtones. Said instruments have radius/length ratios of the order of 0.04:1.
However, when applied to the traditional steelpan the tube which forms the skirt is not, by virtue of the same characteristic uneven frequency response, an optimum acoustic resonator for the simultaneous spectrum of overtones that typically exists for notes on the playing surface. For example, if the length of the skirt is adjusted so that its first resonance corresponds to the pitch of the lowest note on a given drum, then the octave of said note would be suppressed as a consequence of the frequency response minimum. This problem is compounded when one considers the effect of the fifth, which would normally be the other note on the playing surface of a bass, and its partials.
In consequence therefore, all of the above suggests that traditional steelpan construction techniques do not adequately focus on the acoustic design of the instrument and that more effective skirt designs are required.
Regrettably, traditional acoustic steelpans do not allow for the easy removal and replacement of the skirt to facilitate maintenance, transportation, or change in instrument sound radiation characteristics.
Traditional acoustic steelpans are usually suspended from a specially designed stand by a string, cord, or wire. Apart from the need for improvement in terms of aesthetics, this arrangement facilitates undesirable coupling of vibration energy between the steelpan, the support stand and the floor on which it is placed. This unwanted coupling can further detract from musical quality through the additional noise component added, particularly from the support stand, or other such structure.
In addition, as the string, cord, or wire by which the steelpan is suspended is usually affixed to the rim of the instrument, the top of the support stand to which the string is attached must project above the rim and therefore impedes somewhat the performance of the player. As well, although support stands with mechanisms for height adjustments do exist, said traditional method of suspension does not facilitate easy adjustment of the attitude of the instrument. This works against the ergonomic use of the instrument.
U.S. Pat. No. 4,214,404 to Rex is among numerous innovations which describe percussive devices which produce musical sound using acoustic or mechanical means and is a drum comprised of a multiplicity of resonant chambers within a single enclosure and excited by a drum head that effectively forms a compound membrane, when pinched against the opening of said resonant chambers. The said invention thus disclosed, uses acoustic resonance of tubes, as its sound generation mechanism and is therefore different in design from the steelpans that exist in the prior art, or as described, such as that of the present invention, that use the modal characteristics of shell indentations on a continuous surface to produce sound.
Canadian patent No. 1209831 (expired) to Salvador and Peters, provided a drum which was adapted to mitigate the drawbacks found in the prior art structure. More specifically, the said invention provided a drum having a musical note bearing surface, which included rectangular notes which were tunable, to have the harmonic modes of each individual note dominate the inharmonic modes.
German patent No. DE20013648U to Schulz and Weidensdorfer outlines a steel drum which has an outer ring of eight tone fields (1-8) representing an octave (diatonic) from middle C to upper C. It also has an inner so-called centre area containing five tone fields, viz. containing upper D, E and F (9-11) and two areas covering B flat or A sharp and G flat or F sharp. Thus the musical range is a tenth form middle C to E above upper C plus two accidentals i.e. B flat or A sharp and G flat or F sharp.
U.S. Pat. No. 5,814,747 to Ramsell the “Percussion Instrument capable of producing Musical Tone” is a device that is comprised of a multiplicity of synthetic tubes of varying lengths, that resonate at different frequencies when struck with a mallet. The invention thus disclosed is a percussive device that produces musical tones, but uses acoustic resonance of tubes as its sound generation mechanism and is therefore different in design from the steelpans which comprise the prior art, or as described such as that of the present invention, which use the modal characteristics of shell indentations on a continuous surface to produce sound.
U.S. Pat. No. 5,973,247 to Matthews, describes The “Portable Steel Drums and Carrier” a device that is comprised of two steelpan drums with eighteen notes on a harness and mount, designed for the carrying of two steelpan drums mounted upon the human body. The invention thus disclosed does not cover the entire musical range, nor does it extend the range of the traditional steelpan, nor does it give consideration to the optimum design of the playing surface, rim and skirt of the steelpan drums used, nor does it consider the design of the skirt to effect sound propagation.
U.S. Pat. No. 6,750,386 to King, describes The “Cycle of Fifths Steelpan,” a steelpan which uses a note layout based on the cycle of fourths and fifths. The invention thus disclosed, differs from the prior art only by way of the layout of notes, such that they progress in musical fifths intervals in a counter-clockwise direction, whereas the traditional tenor steelpan as well as the invention described in this document places notes progressing in musical fifths intervals in a counter-clockwise direction. The invention thus disclosed does not cover the entire musical range, nor does it extend the range of the traditional steelpan, nor does it give consideration to the optimum design of the playing surface, rim and skirt of the steelpan drums used, nor does it consider the design of the skirt to effect sound propagation.
U.S. Pat. No. 6,212,772 to Whitmyre and Price, the “Production of a Caribbean Steelpan” describes a manufacturing process to facilitate mass production of the steelpan musical instrument by hydroforming the playing surface. The process also allows for providing the instrument with a means to easily detach the skirt to facilitate maintenance, portability and changes in tonal characteristics. However, the description in said aforementioned patent, does not disclose an instrument that extends the range of the traditional steelpan, nor does it reduce the number of steelpans required in an orchestra, nor does it give consideration to the optimum design of the playing surface, rim and skirt of the steelpan drums used for the reduction of non-musical resonances, nor does it consider the design of the skirt to effect sound propagation, nor does it treat with the issue of how the steelpans are to be suspended.
In particular, whereas previously, steelpan quality was subject to the inconsistencies of drums and barrels that could be accessed by tuners, but which were fabricated for the express purpose of packaging, the ensemble of the present invention features a playing surface that is significantly improved through use of certified high quality steels, specifically selected for its manufacture.
In addition, the playing surface is of a compound design to support the creation of notes in the upper musical ranges. The present invention noticeably breaks with the traditional consideration of a drum as an integral entity, treating with said drum, instead, as an item that is constructed from three separate components after deliberate and careful design of said components of the instrument, for optimization of function and in so doing, overcomes the heretofore mentioned disadvantages of the prior art.